1. Field of the Invention
The present invention relates generally to data communication networks, and to techniques for determining bandwidth of communication links between a source and a destination in such data communication networks. More particularly, the present invention relates to the detection of the bandwidth of links between an Internet server and a client computer.
2. Description of Related Art
Networks are utilized extensively to transmit data from one computer system to another. There are many types of networks which are heterogeneous, in that the network has many different types of devices and different types of communication media executing multiple layers of network protocols arranged in stacks for interconnecting the various devices using the diverse media. One example of such a network is the Internet. However, a continuing problem when transmitting data over such networks is the bandwidth of the network. The problem is particularly relevant in connection with the Internet and the World Wide Web, as the Internet becomes a vehicle for delivering a wide variety of resources between servers and clients.
As mentioned above, the Internet is highly heterogeneous. Some devices are connected to the Internet over a standard telephone network modem or a wireless network, with limited bandwidth. Other devices are connected over a high-speed links and have much higher bandwidth capabilities. Users who download graphically rich multimedia objects embedded within Web pages over a lower bandwidth link frequently must wait a significant amount of time for delivery of multimedia objects. This frustrates users of the Internet and results in less use.
For a variety of reasons, it is desirable to detect the bandwidth of a communication link between a server and a client in the Internet, and in other heterogeneous networks. However, the heterogeneity of the network prevents straightforward solutions to this problem. Previous approaches to bandwidth detection in a heterogeneous network include pathchar and bing. (See, “Pathchar—Tool written by Van Jacobson of LBL's Network Research Group.” http://www.caida.org/Pathchar; and “Bing 1.04” http://spengler.econ.duke.edu/˜ferizs/bing.txt.) These previous approaches have several deficiencies. In pathchar, the algorithm attempts to establish bandwidth detection on a link by link basis for a communication channel through the network. This process is impractical because it can take several hours to accurately compute the bandwidth of the channel. Both pathchar and bing are deficient because they do not function if there are firewalls between the server and the client, and return grossly inaccurate measurements if there are proxies between the server and the client.
Accordingly, it is desirable to detect the effective bandwidth between a server and a client quickly and efficiently. Furthermore, it is desirable to provide such detection in widely used heterogeneous networks, such as the Internet.